Fuel cell unit, composite block of fuel cells and method for manufacturing a composite block of fuel cells

ABSTRACT

In order to create a fuel cell unit, comprising a cathode-anode-electrolyte unit and a contact plate which is in electrically conductive contact with the cathode-anode-electrolyte unit, which requires only small production resources and is thus suitable for large-scale production it is suggested that the fuel cell unit comprise a fluid guiding element which is connected to the contact plate in a fluid-tight manner, forms a boundary of a fluid chamber having fluid flowing through it during operation of the fuel cell unit and is designed as a shaped sheet metal part.

The present invention relates to a fuel cell unit which comprises acathode-anode-electrolyte unit and a contact plate which is inelectrically conductive contact with the cathode-anode-electrolyte unit(CAE unit).

Fuel cell units of this type are known from the state of the art.

As a rule, several such fuel cell units are combined to form a compositeblock of fuel cells, in which the fuel cell units follow one anotheralong a stacking direction.

In the cathode-anode-electrolyte unit, an electrochemical reaction takesplace during the operation of the fuel cell unit, during the course ofwhich electrons are supplied to the anode of the CAE unit and electronswithdrawn from the cathode of the CAE unit for the ionization of oxygenatoms. The contact plates arranged between the CAE units of twoconsecutive fuel cell units serve to balance the charge between thecathode of the one fuel cell unit and the anode of the adjacent fuelcell unit in order to supply the cathode with the electrons required forthe ionization. Electric charges may be tapped from the edge-sidecontact plates of the composite block of fuel cells in order to supplythem to an external useful current circuit.

The contact plates used with the known fuel cell units are metal plateswhich are milled or eroded from the entire plate and between which theCAE units are inserted so that these contact plates serve at the sametime to hold the CAE units, as well. Furthermore, these plates areprovided with channels which serve for the passage of fluids(combustible gas, oxidation agent and/or refrigerant) through the fuelcell unit.

These known fuel cell units are very complicated to produce and thussuitable only for small quantities.

The object underlying the present invention is therefore to create afuel cell unit of the type specified at the outset which requires onlysmall production resources and is thus suitable for large-scaleproduction.

This object is accomplished in accordance with the invention, in a fuelcell unit with the features of the preamble to claim 1, in that the fuelcell unit comprises a fluid guiding element which is connected to thecontact plate in a fluid-tight manner, forms a boundary of a fluidchamber having fluid flowing through it during operation of the fuelcell unit and is designed as a shaped sheet metal part.

Such a shaped sheet metal part may be produced from an essentially flatsheet metal blank by means of one or more shaping processes, inparticular, by means of embossing and/or deep drawing. These productionmethods are considerably more suitable and more inexpensive for alarge-scale production than the production of solid metal plates by wayof milling or erosion.

In addition, it is possible to save on material and weight due to theuse of shaped sheet metal parts.

The fluid flowing through the fluid chamber can be a combustible gas, anoxidation agent or a refrigerant.

In particular, it may be provided for the fluid chamber to besurrounded, apart from by the fluid guiding element, by the contactplate and by the cathode-anode-electrolyte unit.

In a preferred configuration of the invention it is provided for thecathode-anode-electrolyte unit of the fuel cell unit to be arranged onthe fluid guiding element.

In particular, it may be provided for the cathode-anode-electrolyte unitto be arranged between the fluid guiding element, on the one hand, andthe contact plate of the same fuel cell unit or an adjacent fuel cellunit, on the other hand.

The inventive fuel cell unit is already particularly simple to handleprior to the assembly of the composite block of fuel cells when thecathode-anode-electrolyte unit is held between the fluid guiding elementand the contact plate of the same fuel cell unit.

Alternatively hereto, it may also be provided for thecathode-anode-electrolyte unit to be designed as a coating on the fluidguiding element or on the contact plate of the fuel cell unit.

It is particularly favorable when not only the fluid guiding element butalso the contact plate is designed as a shaped sheet metal part. In thiscase, the contact plate of the fuel cell unit may also be produced in asimple manner by way of embossing and/or deep drawing from anessentially flat sheet metal blank which is more suitable and moreinexpensive for a large-scale production than the production of solidcontact plates by way of milling or erosion.

The contact plate and the fluid guiding element may, in this case, forma two-part shell of the fuel cell unit which surrounds thecathode-anode-electrolyte unit.

The inventive construction of a fuel cell unit is particularly suitablefor so-called high-temperature fuel cell units which have an operatingtemperature of up to 950° C. and can be operated, without any externalreformer, directly with a hydrocarbonaceous combustible gas, such as,for example, methane or natural gas or alternatively hereto, using anexternal reformer, with a diesel or petroleum motor fuel.

For use in such a high-temperature fuel cell unit the shaped sheet metalparts, from which the fluid guiding element and also, where applicable,the contact plate of the fuel cell unit are formed, are produced from asheet metal material which is chemically resistant at the resultingtemperatures of up to 950° C. in relation to the components of thecombustible gas, the combustion air supplied and a refrigerant suppliedwhere applicable (for example cooling air).

High-grade steel sheets resistant to high temperatures or steel sheetscoated with an inorganic or ceramic material are particularly suitablefor this purpose.

Furthermore, a sheet metal material is preferably selected which has athermal coefficient of expansion compatible with that of the CAE unit.

The thickness of the sheet metal material used is preferably at the mostapproximately 3 mm, in particular, at the most approximately 1 mm.

In order to achieve a reliable connection between the contact plate andthe fluid guiding element of the same fuel cell unit which is alsoresistant and gas-tight at high temperatures, it is preferably providedfor the fluid guiding element and the contact plate to be connected toone another by way of welding, preferably by laser welding or byelectron beam welding.

Alternatively or in addition hereto it may be provided for the fluidguiding element and the contact plate to be connected to one another byway of soldering, preferably by hard soldering.

In order to make the required compensation of charges between the CAEunits of fuel cell units adjacent to one another possible in a simplemanner it is provided in a preferred configuration of the inventive fuelcell unit for the fluid guiding element to have an opening for thepassage of contact elements (e.g. of an adjacent fuel cell unit) to thecathode-anode-electrolyte unit.

In order to be able to hold the CAE unit between the fluid guidingelement and the contact element of the fuel cell unit without shortingthe anode and the cathode of the same fuel cell unit with one another,it is advantageously provided for the fluid guiding element to abut onthe cathode-anode-electrolyte unit via an electrically insulating seal.

In a preferred configuration of the invention, the fluid guiding elementis designed as a fluid guiding frame which abuts on thecathode-anode-electrolyte unit along the entire edge thereof via theelectrically insulating seal.

It is particularly favorable when the seal between the fluid guidingelement and the CAE unit comprises mica.

Alternatively or in addition hereto, it may be provided for the sealbetween the CAE unit and the fluid guiding element to comprise a flatseal.

Alternatively or in addition hereto, it may be provided for the sealbetween the CAE unit and the fluid guiding element to comprise a coatingon the fluid guiding element and/or on the cathode-anode-electrolyteunit.

Such a coating may be applied, for example, by the screen printingmethod, by roller coating or by spray coating onto the fluid guidingelement or the cathode-anode-electrolyte unit.

Inorganic or ceramic sealing media, which are chemically resistant,gas-tight and electrically insulating at an operating temperature of upto 950° C., can be considered, in particular, for the sealing.

A solder glass can, for example, be used as sealing medium and this canbe composed, for example, like a solder glass known from EP 0 907 215A1, i.e. can contain 11 to 13% by weight of aluminum oxide (Al₂O₃), 10to 14% by weight of boron oxide (BO₂), approximately 5% by weight ofcalcium oxide (CaO), 23 to 26% by weight of barium oxide (BaO) andapproximately 50% by weight of silicon oxide (SiO₂).

Furthermore, it may be provided for the seal between the CAE unit andthe fluid guiding element to be designed as a movable seal (slide fitsealing).

Furthermore, it may be provided for the fluid guiding element to beconnected to the CAE unit by way of flanging.

It may, in particular, be provided for a flange fold area engagingaround the CAE unit to be formed on the fluid guiding element.

In order to obtain the required pressing force for the sealing betweenthe CAE unit and the fluid guiding element irrespective of any externalbiasing of the fuel cell units against one another, it is preferablyprovided for the cathode-anode-electrolyte unit and the fluid guidingelement to already be biased elastically against one another on accountof the geometry of the fuel cell unit and the connection between thefluid guiding element and the contact plate of the fuel cell unit.

In order to be able to use the fluid guiding element, apart from forholding the CAE unit, also for the formation of fluid channels, throughwhich a fluid is supplied to the fuel cell unit or discharged from thesame, it is provided in a preferred configuration of the invention forthe fluid guiding element to be provided with at least one fluid port.

The area of the fluid guiding element surrounding the fluid port servesin this case as fluid guiding area of the fluid guiding element. A fluidchannel then results from the fluid guiding areas of the fluid guidingelements of fuel cell units following one another in the stackingdirection.

The fluid supplied or discharged via the fluid channel can be anoxidation agent or, preferably, a combustible gas.

It is particularly favorable when the holding means is provided with afluid supply channel opening and with a fluid discharge channel opening.In this case, the fluid guiding element can be used not only for theformation of a fluid supply channel but also for the formation of afluid discharge channel.

In order, during the formation of such fluid channels, to maintain therequired electric insulation between the contact plates and fluidguiding elements of adjacent fuel cell units, it is advantageouslyprovided for the fuel cell unit to comprise an electrically insulatingfluid channel seal, via which the contact plate of the fuel cell unitabuts on the fluid guiding element of an adjacent fuel cell unit.

Alternatively or in addition hereto it may also be provided for the fuelcell unit to comprise a fluid channel seal, via which the fluid guidingelement of the fuel cell unit abuts on the contact plate of an adjacentfuel cell unit.

Such a fluid channel seal may, for example, comprise a coating on thefluid guiding element and/or on the contact plate.

Such a coating may be applied, in particular, by the screen printingmethod, by roller coating or spray coating onto the fluid guidingelement or the contact plate, respectively.

Inorganic and ceramic materials, which are chemically resistant,gas-tight and electrically insulating at the resulting operatingtemperatures of up to 950° C., can be considered, in particular, assealing media.

A particularly simple construction of the fluid channel seal resultswhen this comprises a flat seal.

Particularly when the holding plate and the contact plate are connectedto one another by flanging, it is of advantage when the fluid channelseal comprises at least two separate sealing elements which can bearranged, in particular, in different planes.

In order to compensate for different heat expansions, it is particularlyfavorable when the fluid channel seal comprises a slide fit sealing.

Particularly with a design as slide fit sealing it is of advantage whenthe fluid channel seal comprises a material, preferably a solder glass,viscous at the operating temperature of the fuel cell unit.

Claim 20 is directed to a composite block of fuel cells which comprisesa plurality of inventive fuel cell units which follow one another alonga stacking direction.

In order to be able to fix the individual fuel cell units of thecomposite block of fuel cells in their position relative to one anotherand, where required, to be able to generate an adequate contact pressurefor the sealing between the CAE unit and the fluid guiding elementand/or for the sealing between the fluid guiding element and the contactplate of an adjacent fuel cell unit, it is favorable when the compositeblock of fuel cells comprises at least one clamping element for bracingthe fuel cell units against one another.

The composite block of fuel cells can, in particular, comprise two endplates which can be braced against one another by means of the clampingelement.

In order to be able to supply a fluid (combustible gas, oxidation agentor refrigerant) to the composite block of fuel cells in a simple manneror discharge the fluid out of the composite block of fuel cells it isadvantageously provided for at least one of the end plates to have atleast one fluid port.

Bracing of the fuel cell units of the composite block of fuel cellsagainst one another by means of a separate clamping element issuperfluous when it is advantageously provided for the fluid guidingelement of at least one of the fuel cell units to be connected to thecontact plate of an adjacent fuel cell unit by way of flanging. Thisflanging is sufficient to secure the fuel cell units in their positionrelative to one another.

Nevertheless, an additional clamping element can be used in such a caseto generate the contact pressure between the CAE units and the contactplates of the composite block of fuel cells.

It may, in particular, be provided for a flange fold area engagingaround the contact plate of the adjacent fuel cell unit to be formed onthe fluid guiding element of at least one of the fuel cell units.

Alternatively hereto, it may also be provided for a flange fold areaengaging around the fluid guiding element of the adjacent fuel cell unitto be formed on the contact plate of at least one of the fuel cellunits.

In a preferred configuration of the composite block of fuel cells it isprovided for an electrically insulating fluid channel seal to bearranged between the flange fold area and the contact plate of theadjacent fuel cell unit. As a result of the flanging, such a fluidchannel seal is already subject to the contact pressure required for anadequate sealing without any force of an external clamping system beingrequired for this purpose.

In order to produce a composite block of fuel cells which comprises aplurality of inventive fuel cell units, a method is suitable whichcomprises the following method steps:

-   -   Assembly of the individual fuel cell units by arranging a        cathode-anode-electrolyte unit between a contact plate and a        fluid guiding element and gas-tight connection of the contact        plate to the fluid guiding element;    -   subsequent assembly of the composite block of fuel cells by        arranging a plurality of fuel cell units along a stacking        direction and fixing the fuel cell units in their position        relative to one another.

With such a method, the individual parts contact plate, CAE unit andfluid guiding element of a respective fuel cell unit are first of allfitted together and the contact plate and the fluid guiding element areconnected to one another, for example, by welding or soldering in orderto assemble the individual fuel cell unit.

Subsequently, the assembly of the entire composite block of fuel cellstakes place, with which the fuel cell units of the composite block offuel cells are preferably braced against one another by means of atleast one clamping element.

In a special configuration of the method it may be provided for the fuelcell units of the composite block of fuel cells to be arranged betweentwo end plates and for the two end plates to be braced against oneanother.

The method described above is suitable for the production of thecomposite block of fuel cells, in particular, when the fluid guidingelement of at least one fuel cell unit abuts on the contact plate of anadjacent fuel cell unit via a flat seal or a slide fit sealing.

If, on the other hand, in the composite block of fuel cells to beproduced the fluid guiding element of one fuel cell unit is connected tothe contact plate of an adjacent fuel cell unit by way of flanging, amethod which comprises the following method steps is particularlysuitable for the production of such a composite block of fuel cells:

-   -   Assembly of several fluid guiding element-contact plate units by        connecting a respective fluid guiding element of one fuel cell        unit to a contact plate of an adjacent fuel cell unit by way of        flanging;    -   formation of a stack consisting of fluid guiding element-contact        plate units following one another along a stacking direction,        wherein one respective cathode-anode-electrolyte unit is        arranged between two such respective units;    -   gas-tight connection of the contact plates of the fuel cell        units to the respective fluid guiding element of the same fuel        cell unit.

With this method for the production of the composite block of fuelcells, the fluid guiding element of a first fuel cell unit is first ofall preassembled with the contact plate of a second fuel cell unit byway of flanging, preferably at the combustible gas channel and at thedischarge gas channel, wherein electrically insulating fluid channelseals are integrated into the respective flangings. Subsequently, thefinal assembly of the composite block of fuel cells is carried out inthat the CAE units are arranged each time between the consecutive fluidguiding element-contact plate units and the contact plates and fluidguiding elements belonging to the same fuel cell unit, which hold arespective CAE unit between them, are connected to one another in agas-tight manner by way of welding or soldering.

Additional features and advantages of the invention are the subjectmatter of the following description and drawings illustratingembodiments. In the drawings:

FIG. 1 shows a schematic perspective illustration of a fuel cell devicewith supply lines and discharge lines for the oxidation agent and thecombustible gas;

FIG. 2 shows a schematic longitudinal section through a composite blockof fuel cells arranged in the housing of the fuel cell device from FIG.1;

FIG. 3 shows a schematic longitudinal section through acathode-anode-electrolyte unit with contact plates adjoining thereto;

FIG. 4 shows a schematic perspective exploded illustration of two fuelcell units of the composite block of fuel cells from FIG. 2 followingone another in a stacking direction;

FIG. 5 shows a schematic plan view of a contact plate of one of the fuelcell units from FIG. 4;

FIG. 6 shows a schematic plan view of a fluid guiding frame of one ofthe fuel cell units from FIG. 4;

FIG. 7 shows the right-hand part of a schematic cross section throughthree fuel cell units of the composite block of fuel cells from FIG. 2following one another in the stacking direction;

FIG. 8 shows the right-hand part of a schematic longitudinal sectionthrough three fuel cell units of the composite block of fuel cells fromFIG. 2 following one another along the stacking direction in a firstembodiment of the composite block of fuel cells, with which a fluidguiding frame of a fuel cell unit abuts via a flat seal on acathode-anode-electrolyte unit (CAE unit) of the same fuel cell unit andvia an additional flat seal on the contact plate of an adjacent fuelcell unit;

FIG. 9 shows a schematic longitudinal section corresponding to FIG. 8through three fuel cell units following one another along the stackingdirection in a second embodiment of the composite block of fuel cells,with which the fluid guiding frame of one fuel cell unit is connected tothe contact plate of an adjacent fuel cell unit by way of flanging;

FIG. 10 shows a schematic longitudinal section corresponding to FIG. 8through three fuel cell units following one another along the stackingdirection in a third embodiment of the composite block of fuel cells,with which the fluid guiding frame of one fuel cell unit is connected tothe CAE unit of the same fuel cell unit by way of flanging and to thecontact plate of an adjacent fuel cell unit likewise by flanging;

FIG. 11 shows a schematic longitudinal section corresponding to FIG. 8through three fuel cell units following one another along the stackingdirection in a fourth embodiment of the composite block of fuel cells,with which the fluid guiding frame of one fuel cell unit is connected tothe contact plate of an adjacent fuel cell unit via a slide fit sealing;and

FIG. 12 shows a schematic longitudinal section corresponding to FIG. 8through three fuel cell units following one another along the stackingdirection in a fifth embodiment of the composite block of fuel cells,with which the fluid guiding frame of one fuel cell unit is connected tothe CAE unit of the same fuel cell unit and to the contact plate of anadjacent fuel cell unit via a respective slide fit sealing.

The same or functionally equivalent elements are designated in all theFigures with the same reference numerals.

A fuel cell device illustrated in FIGS. 1 to 8 and designated as a wholeas 100 comprises an essentially parallelepiped housing 102 (cf. FIG. 1),into which a supply line 104 for oxidation agent opens, via which anoxidation agent, for example, air or pure oxygen is supplied to theinterior of the housing 102 by a supply blower (not illustrated) at anoverpressure of, for example, approximately 50 millibars.

Furthermore, a discharge line 105 for oxidation agent, through whichsuperfluous oxidation agent can be discharged from the interior of thehousing 102, opens into the housing 102.

A composite block of fuel cells 106 illustrated as a whole in FIG. 2 isarranged in the interior of the housing 102 and comprises a lower endplate 108, an upper end plate 110 and a plurality of fuel cell units 114which are arranged between the lower end plate 108 and the upper endplate 100 and follow one another along a stacking direction 112.

As is best apparent from FIG. 4, which shows a perspective, explodedillustration of two fuel cell units 114 following one another along thestacking direction 112, each of the fuel cell units 114 comprises anessentially plate-like cathode-anode-electrolyte unit 116 (abbreviatedin the following to: CAE unit) which is held between a contact plate 118and a fluid guiding frame 120.

The CAE unit 116 comprises, as illustrated purely schematically in FIG.3, a gas-permeable, electrically conductive support layer 121 which canbe designed, for example, as a mesh or net consisting of a metallicmaterial, e.g. of nickel, through the openings in which a combustiblegas can pass from a chamber 124 for combustible gas adjoining thesupport layer 121.

Furthermore, the CAE unit 116 comprises a plate-like anode 122 which isarranged on the support layer 121 and consists of an electricallyconductive, ceramic material, such as, for example, Ni—ZrO₂ ceramet(ceramic-metal mixture), which is porous in order to enable thecombustible gas from the chamber 124 for combustible gas to pass throughthe anode 122 to the electrolyte 126 adjoining the anode 122.

A hydrocarbonaceous gas mixture or pure hydrogen can be used, forexample, as combustible gas.

The electrolyte 126 is preferably designed as a solid electrolyte andformed, for example, from a yttrium-stabilized circonium dioxide.

On the side of the electrolyte 126 located opposite the anode 122 aplate-like cathode 128 borders thereon, which is formed from anelectrically conductive, ceramic material, for example, from LaMnO₃ andhas a porosity in order to enable an oxidation agent, for example, airor pure oxygen to pass to the electrolyte 126 from a chamber 130 foroxidation agent adjoining the cathode 128.

During operation of the fuel cell device 100 the CAE unit 116 of eachfuel cell unit 114 has a temperature of, for example, approximately 850°C., at which the electrolyte 126 is conductive for oxygen ions. Theoxidation agent from the chamber 130 for oxidation agent absorbselectrons at the anode 122 and releases bivalent oxygen ions to theelectrolyte 126 which migrate through the electrolyte 126 to the anode122. At the anode 122, the combustible gas from the chamber 124 forcombustible gas is oxidized by the oxygen ions from the electrolyte 126and thereby releases electrons to the anode 122.

The contact plates 118 serve to draw off from the anode 122 via thesupport layer 121 the electrons released during the reaction at theanode 122 or rather feed to the cathode 128 the electrons required forthe reaction at the cathode 128.

For this purpose, each of the contact plates 118 consists of a metalsheet which is a good electrical conductor and is provided (as best seenfrom FIG. 5) with a plurality of contact elements 132 which have, forexample, the shape of projections and recesses which adjoin one another,have a respectively square design and are formed by the superposition ofa first wave pattern with wave troughs and crests directed parallel tothe narrow sides 133 of the contact plate 118 and a second wave patternwith wave troughs and crests directed parallel to the longitudinal sides135 of the contact plate 118.

The contact field 134 of the contact plate 118 formed from the contactelements 132 thus has the structure of corrugated metal corrugated intwo directions at right angles to one another.

The contact elements 132 are arranged on the respective contact plate118 in a square grating, wherein contact elements adjacent to oneanother project alternatingly to different sides of the contact plate118 from the central plane 139 of the contact plate 118. The contactelements on the anode side projecting from the contact plate 118 upwardsand thus to the anode 122 of the CAE unit 116 belonging to the same fuelcell unit 114 are designated with the reference numeral 132 a, thecontact elements on the cathode side projecting from the contact plate118 downwards and thus to the cathode 128 of the CAE unit 116 belongingto an adjacent fuel cell unit 114 are designated with the referencenumeral 132 b.

The dash-dot lines drawn in in FIG. 5 within the contact field 134reproduce the boundary lines of the contact elements 132, along whichthe contact plate 118 intersects their central plane 139.

Each of the contact elements 132 has a central contact area 137, atwhich it is in electrically conductive contact with an adjoining CAEunit 116.

The contact areas 137 of the anode-side contact elements 132 a of acontact plate 118 are in electrical point contact with the support layer121 and thus with the anode 122 of the CAE unit 116 belonging to thesame fuel cell unit 114 so that electrons can pass from the respectiveanode 122 to the contact plate 118.

The cathode-side contact elements 132 b of the contact plates 118 are inelectrically conductive point contact with the cathode 128 of the CAEunit 116 belonging to an adjacent fuel cell unit 114 so that electronscan pass from the contact plate 118 to the cathode 128. In this way thecontact plates 118 make a charge compensation possible between theanodes 122 and cathodes 128 along the stacking direction 112 ofconsecutive CAE units 116.

The contact plates 118 arranged at the ends of the composite block offuel cells 106 are (in a manner not illustrated in the drawings)connected to an external current circuit in order to tap the electricalchanges resulting at these edge-side contact plates 118.

As is best apparent from the plan view of FIG. 5, the central,rectangular contact field 134 of each contact plate 118 provided withthe contact elements 132 is surrounded by a flat flange area 136 whichforms the outer edge of the contact plate 118 and is aligned parallel tothe central plane 139 of the contact field 134 but in relation to thisis displaced towards the CAE unit 116 so that in the area of the narrowlongitudinal sides 138 of the flange area 136 the underside of the CAEunit 116 rests on the upper side of the flange area 136 (cf., inparticular, FIG. 7).

The broad side areas 140 of the flange area 136 each have a port 142 and144, respectively, which enable the passage of combustible gas to besupplied to the fuel cell units 114 or of waste gas to be dischargedfrom the fuel cell units 114, this waste gas containing superfluouscombustible gas and products of combustion, in particular, water.

The flange area 136 is connected to the contact field 134 arranged so asto be offset hereto via an inclined surface 146 which surrounds thecontact field 134 and adjoins the contact field 134 at a first bendingline 148 and the flange area 136 at a second bending line 150.

Each of the contact plates 118 is designed as a shaped sheet metal partwhich is formed from an essentially flat, essentially rectangular layerof sheet metal by way of embossing and/or deep drawing as well as bypunching or cutting out the ports 142, 144.

The fluid guiding frames 120 are also formed as shaped sheet metal partsfrom an essentially flat, essentially rectangular sheet metal layer.

As is best seen in FIG. 6, each fluid guiding frame 120 has at its endareas 152 ports corresponding to the ports 142, 144 in the contactplates 118, namely a combustible gas port 154 and a waste gas port 156.

As is best seen from FIGS. 6 and 8, each of the ports 154, 156 in afluid guiding frame 120 is surrounded by a collar 158 extending alongthe stacking direction 112, a seal contact area 162 adjoining the collar158 along a bending line 160 and extending away from the port at rightangles to the stacking direction 112 and a channel wall area 166adjoining the seal contact area 162 at a bending line 164 and beingaligned parallel to the stacking direction 112. Where the channel wallarea 166 adjoins an outer edge of the frame 120 it merges at a bendingline 167 into a flange area 168 aligned at right angles to the stackingdirection 112.

As is best seen from FIG. 6, each of the fluid guiding frames 120 hasbetween the ports 154, 156 in the end areas 152 of the fluid guidingframe 120 an essentially rectangular, central opening 170 for thepassage of the contact elements 132 of the contact plate 118 of anadjacent fuel cell unit 114.

As is apparent from FIGS. 6 and 8, the channel wall area 166, where itis adjacent to the opening 170, merges at a bending line 172 into aninner edge area 178 of the fluid guiding frame 120 aligned at rightangles to the stacking direction 112.

As is best seen from FIG. 6, the inner edge area 178 of the fluidguiding frame 120 extends all around the opening 170.

In the narrow longitudinal areas 180 of the fluid guiding frame 120,which are arranged between the openings 170 and the outer edge of thefluid guiding frame 120 and connect the two end areas 152 of the fluidguiding frame 120 with one another, the inner edge area 178 merges atits edge facing away from the opening 170 along a bending line 182 intoa vertical wall area 184 which is aligned parallel to the stackingdirection 112 and, for its part, merges along a bending line 185 intothe flange area 168 forming the outer edge of the fluid guiding frame120.

As is best seen from FIGS. 4 and 8, each CAE unit 116 is provided at theedge of its upper side facing the fluid guiding frame 120 of the samefuel cell unit 114 with a gas-tight, electrically insulating combustiblegas chamber seal 186 which projects laterally beyond the CAE unit 116.

The combustible gas chamber seal may comprise, for example, a flat sealconsisting of mica.

Alternatively or in addition hereto it may also be provided for thecombustible gas chamber seal 186 to comprise a gas-tight, electricallyinsulating coating on the underside of the fluid guiding frame 120 whichis applied to the underside of the inner edge area 178 of the fluidguiding frame 120 by way of the screen printing method or by means ofroller coating.

As is best seen from FIG. 8, the two seal contact areas 162 surroundingthe ports 154, 156 of the fluid guiding frame 120 are provided with arespective gas channel seal 188 on their upper side facing away from theCAE unit 116.

The gas channel seal 188 also preferably comprises a flat sealconsisting of mica or a gas-tight, electrically insulating coating whichcan be applied to the seal contact area 162 of the fluid guiding frame120 as a paste by way of the screen printing method or by means ofroller coating.

In the assembled state of a fuel cell unit 114, the CAE unit 116 of therelevant fuel cell unit 114 abuts with its support layer 121 on theanode-side contact elements 132 a of the contact plate 118 of the fuelcell unit 114.

The fluid guiding frame 120 of the fuel cell unit 114 abuts, for itspart, via the combustible gas chamber seal 186 on the outer edge of thecathode 128 of the CAE unit 116 and with the flange area 168 on theflange area 136 of the contact plate 118.

The flange area 168 and the flange area 136 are secured to one anotherby way of welding (e.g. the laser welding method or the electron beammethod) or by soldering, in particular, a hard soldering and sealed in agas-tight manner.

The fuel cell units 114 of the composite block of fuel cells 106 arestacked on top of one another along the stacking direction 112 such thatthe cathode-side contact elements 132 b of each contact plate 118 extendthrough the openings 170 in the fluid guiding frame 120 of therespective fuel cell unit 114 arranged therebelow to the cathode of theCAE unit 116 of the fuel cell unit 114 arranged therebelow and abutthereon in electrically conductive contact.

The flange area 136 of each contact plate 118 thereby abuts on the gaschannel seal 188 of the fluid guiding frame 120 of the respective fuelcell unit 114 arranged therebelow, wherein the collar 158, whichsurrounds the respective port 154 or 156 in the fluid guiding frame 120,extends into the respectively corresponding port 142 or 144 of thecontact plate 118.

The end area 152 of each fluid guiding frame 120 surrounding thecombustible gas port 154 forms a combustible gas guiding area. The endarea 152 of each fluid guiding frame 120 surrounding the waste gas port156 forms a waste gas guiding area.

As is best seen from the sectional illustration of FIG. 2, thecombustible gas guiding areas of the fluid guiding frames 120 whichfollow one another along the stacking direction 112 together form acombustible gas channel 190 which extends parallel to the stackingdirection 112 and at its upper end opens in a recess 192 on theunderside of the upper end plate 110.

At the lower end of the combustible gas channel 190, a combustible gassupply opening 194 opens into it which passes through the lower endplate 108 of the composite block of fuel cells 106 coaxially to thecombustible gas channel 190.

A combustible gas supply line 196 is connected to the end of thecombustible gas supply opening 194 facing away from the combustible gaschannel 190, this supply line being guided through the housing 102 ofthe fuel cell device 100 in a gas-tight manner and being connected to acombustible gas supply (not illustrated) which supplies to thecombustible gas supply line 196 a combustible gas, for example, ahydrocarbonaceous gas or pure hydrogen at an overpressure of, forexample, approximately 50 millibars.

As is likewise best seen from FIG. 2, the waste gas guiding areas of thefluid guiding frames 120 following one another along the stackingdirection 112 together form a waste gas channel 198 which is alignedparallel to the stacking direction 112 and at its lower end is closed bya projection 200 provided on the upper side of the lower end plate 108of the composite block of fuel cells 106.

At its upper end the waste gas channel 198 opens into a waste gasdischarge opening 202 which is coaxial thereto, passes through the upperend plate 110 of the composite block of fuel cells 106 and at its endfacing away from the waste gas channel 198 is connected to a waste gasdischarge line 204.

The waste gas discharge line 204 is guided through the housing 102 ofthe fuel cell device 100 in a gas-tight manner and connected to a wastegas treatment unit (not illustrated).

During operation of the fuel cell device 100 the combustible gas flowsthrough the combustible gas supply line 196 and the combustible gassupply opening 194 into the combustible gas channel 190 and isdistributed from there through the intermediate spaces between thecontact plates 118 and the respective fluid guiding frames 120 belongingto the same fuel cell unit 114 to the combustible gas chambers 124 ofthe fuel cell units 114 which are each surrounded by the contact plate118, the fluid guiding frame 120 and the CAE unit 116 of the relevantfuel cell unit 114.

As already described, the combustible gas is oxidized at least partiallyat the anode 122 of the respective CAE unit 116 limiting the respectivecombustible gas chamber 124.

The product of oxidation (for example, water) passes together withsuperfluous combustible gas out of the combustible gas chambers 124 ofthe fuel cell units 114 into the waste gas channel 198, from which it isdischarged through the waste gas discharge opening 202 and the waste gasdischarge line 204 to the waste gas treatment unit (not illustrated).

In the waste gas treatment unit, the product of reaction (for example,water) is, for example, removed from the stream of waste gas andsuperfluous combustible gas is conducted to the combustible gas supplyin order to be supplied again to the fuel cell device 100.

The oxidation agent required for the operation of the fuel cell device100 (for example, air or pure oxygen) is supplied to the interior of thehousing 102 through the oxidation agent supply line 104.

In the interior of the housing 102, the oxidation agent is distributedto the oxidation agent chambers 130 which are formed between thecombustible gas chambers 124 of the fuel cell units 114 and which aresurrounded by a respective contact plate 118 of a fuel cell unit 114 aswell as by the fluid guiding frame 120 and the cathode 128 of the CAEunit 116 of an adjacent fuel cell unit 114.

The oxidation agent passes into the oxidation agent chambers and out ofthem again by way of the intermediate spaces between a respective fluidguiding frame 120 of a fuel cell unit 114 and the contact plate 118 ofthe fuel cell unit 114 following thereon in the stacking direction 112.

As already described, oxygen ions are formed from the oxidation agent atthe cathodes 128 of the CAE units 116 of the fuel cell units 114 andthese migrate through the electrolytes 126 to the anodes 122 of the CAEunits 116 of the fuel cell units 114.

Superfluous oxidation agent passes out of the oxidation agent chambers130 of the fuel cell units 114 on the exit side located opposite theentry side of the oxidation agent and is discharged from the interior ofthe housing 102 of the fuel cell device 100 through the oxidation agentdischarge line 105.

The direction of flow of the combustible gas and the waste gas throughthe fuel cell device 100 is specified in the drawings with single arrows210, the direction of flow of the oxidation agent through the fuel celldevice 100 by means of double arrows 212.

The direction of flow of the oxidation agent through the oxidation agentchambers 130 is essentially at right angles to the direction of flow ofthe combustible gas through the combustible gas chambers 124.

In order to secure the fuel cell units 114 following one another alongthe stacking direction 112 against one another by way of externalclamping, several connecting screws 214 are provided which pass throughbores 216 in the end plates 108, 110 of the composite block of fuelcells 106 and are provided at their end facing away from the respectivescrew head 218 with an external thread 220, into which a respectivecoupling nut 222 is turned so that the end plates 108, 110 are clampedbetween the screw heads 218 and the connecting nuts 222 and a desiredpressing force can be transferred via the end plates 108, 110 onto thestack of fuel cell units 114 (cf. FIG. 2).

The pressing force generated by the external clamping by means of theconnecting screws 214 and connecting nuts 222 determines the contactpressure, with which the flange areas 136 of the contact plates 118 arepressed against the gas channel seals 188 on the fluid guiding frames120.

The contact pressure, with which the fluid guiding frames 120 arepressed against the combustible gas chamber seals 186 on the CAE units116, is, on the other hand,—irrespective of the external clamping bymeans of the connecting screws 214 and connecting nuts 222—determinedexclusively by the elastic biasing force, with which the fluid guidingframe 120 of a fuel cell unit 114 is biased against the CAE unit 116 ofthe same fuel cell unit 114.

This elastic biasing is generated at the point of time, at which thefluid guiding frame 120 and the contact plate 118 of the same fuel cellunit 114 are secured against one another at the flange areas 136 and168, respectively. This elastic biasing force is dependent on thegeometry of the fuel cell units 114 and is brought about due to the factthat the sum of the extensions of a contact element 132 a and the CAEunit 116 with the combustible gas chamber seal 186 arranged thereon inthe stacking direction 112 is somewhat greater than the distance theunderside of the inner edge area 178 of the fluid guiding frame 120would take up from the central plane of the contact field 134 of thecontact plate 118 in the non-deformed state of the fluid guiding frame120. As a result of the CAE unit 116 clamped between the contact plate118 and the fluid guiding frame 120, the fluid guiding frame 120 isdeformed elastically which results in an elastic restoring force whichbiases the fluid guiding frame 120 against the CAE unit 116.

The composite block of fuel cells 106 described above is mounted asfollows:

First of all, the individual fuel cell units 114 are mounted in that aCAE unit 116 is arranged each time between a contact plate 118 and afluid guiding frame 120 and, subsequently, the flange areas 136 of thecontact plate 118 abutting against one another as well as the flangearea 168 of the fluid guiding frame 120 are connected to one another ina gas-tight manner, for example, by welding or soldering, in particular,hard soldering. Subsequently, the composite block of fuel cells 106 isassembled from the individual fuel cell units 114 in that the desirednumber of fuel cell units 114 is stacked along the stacking direction112 and the fuel cell units 114 are fixed in their position relative toone another by means of the end plates 108, 110 and the connectingscrews 214 and connecting nuts 222 bracing the end plates against oneanother.

A second embodiment of a fuel cell device 100 illustrated in FIG. 9differs from the first embodiment described above in that the contactplates 118 do not merely abut on the fluid guiding frame 120′ of anadjacent fuel cell unit 114 in the area of the gas channel seals 188 butrather are connected to this fluid guiding frame by way of flanging.

As is apparent from FIG. 9, the collar 158′ of each fluid guiding frame120′ passes through the waste gas port 144 (or the combustible gas port142) in the contact plate 118 of the adjacent fuel cell unit 114 andmerges at a bending line 224 into a flange fold area 226 aligned atright angles to the stacking direction 112.

The gas channel seal 188′ arranged on the side of the fluid guidingframe 120′ facing the contact plate 118 is designed, in this secondembodiment, not in one piece as in the first embodiment described abovebut in two pieces and comprises a first flat seal 228, which is arrangedbetween the upper side of the seal contact area 126 of the fluid guidingframe 120′ and the underside of the flange area 136 of the contact plate118, and a second flat seal 230 which is arranged between the undersideof the flange fold area 226 of the fluid guiding frame 120′ and theupper side of the flange area 136 of the contact plate 118.

The flat seals 228, 230 may be designed as mica seals or as gas-tight,electrically insulating coatings (on the contact plate 118 or on thefluid guiding frame 120′).

The flange fold area 226 on the fluid guiding frame 120′ forms anundercut, as a result of which the contact plate 118 of the respectivelyadjacent fuel cell unit 114 is secured on the fluid guiding frame 120′.

In order to reduce the clearance between the contact plate 118 and thefluid guiding frame 120′ at right angles to the stacking direction 112,a spacer ring consisting of an elastically insulating, preferablyceramic material can be arranged in the intermediate space between theedge of the flange area 136 of the contact plate and the collar 158′ ofthe fluid guiding frame 120′.

In this second embodiment, the contact pressure at the gas channel seal188′ required for sealing the waste gas channel 198 and the combustiblegas channel 190, respectively, is not first generated by the externalclamping of the fuel cell units 114 against one another by means of theend plates 108, 110 and the connecting screws 214 and connecting nuts222 arranged thereon but is already determined during the assembly ofthe stack consisting of fuel cell units 114 due to the flanging of theflange area 136 of each contact plate 118 to the fluid guiding frame120′ of the adjacent fuel cell unit 114.

As is apparent from FIG. 9, the inclined surface 146 between the contactfield 134 and the flange area 136 of the contact plate 118 is dispensedwith in this second embodiment and so the flange area 136 of the contactplate 118 is located approximately at the same level as the centralplane 139 of the contact plate 118. Furthermore, the channel wall area166′ of the fluid guiding frame 120′ is not, as in the first embodiment,aligned parallel to the stacking direction 112 but rather is inclined inrelation to the stacking direction 112 through an angle of approximately45°. Moreover, the extension of the channel wall area 166′ along thestacking direction 112 is smaller than in the first embodiment.

The composite block of fuel cells 106 of the second embodiment of a fuelcell device 100 is preferably produced in accordance with the methoddescribed in the following:

First of all, several fluid guiding element-contact plate units arepreassembled in that a fluid guiding frame 120′ of a fuel cell unit 114is connected each time to the contact plate 118 of an adjacent fuel cellunit by way of flanging in the area of the combustible gas channel 190and the waste gas channel 198.

Subsequently, a stack consisting of fluid guiding element-contact plateunits following one another along the stacking direction 112 is formed,wherein one respective CAE unit is arranged between two such units eachtime such that the cathode 128 of the relevant CAE unit 116 abuts on afluid guiding frame 120′ via the combustible gas chamber seal 186.

Furthermore, the stack consisting of the fluid guiding frame-contactplate units is formed such that each contact plate 118 abuts with itsflange area 136 on the flange area 168 of the fluid guiding frame 120′of an adjacent fluid guiding frame-contact plate unit.

Subsequently, the flange areas 136 of the contact plates 118 areconnected to the flange areas 168 of the respective fluid guiding frames120′ belonging to the same fuel cell unit 114 in a gas-tight manner, forexample, by welding or by soldering, in particular, by hard soldering.

As for the rest, the second embodiment of a fuel cell device correspondswith respect to construction and operation to the first embodiment andin this respect reference is made to the preceding description thereof.

A third embodiment of a fuel cell device illustrated in FIG. 10 differsfrom the second embodiment described above in that the holding plates donot merely abut on the CAE units 116 in the area of the combustible gaschamber seal 186 but rather are connected to these CAE units 116 by wayof flanging.

As is apparent from FIG. 10, in this embodiment a contact area 236aligned at right angles to the stacking direction 112 adjoins the sealcontact area 126 of the fluid guiding frame 120′ along a bending line234, this contact area abutting with its upper side areally on theunderside of the seal contact area 126 and, for its part, merging at abending line 238 into a channel wall area 166 aligned parallel to thestacking direction 112.

A flange fold area 240 adjoins the lower edge of the channel wall area166 along a bending line 238, is aligned at right angles to the stackingdirection 112 and abuts with its upper side on the underside of thesupport layer 121 of the CAE unit 116.

The flange fold area 240 on the fluid guiding frame 120′ forms anundercut, as a result of which the CAE unit 116 is secured on the fluidguiding frame 120′ of the same fuel cell unit 114.

In this third embodiment, the contact pressure at the combustible gaschamber seal 186 required for sealing the combustible gas chamber 124 isnot—as in the first two embodiments—determined by the relativeextensions of the contact elements 132 and the fluid guiding frame alongthe stacking direction 112 but is generated directly as a result of theflanging about the CAE unit 118 by the fluid guiding frame 120′.

As for the rest, the third embodiment of a fuel cell device correspondswith respect to construction and operation to the second embodiment andin this respect reference is made to its description above.

A fourth embodiment of a fuel cell device illustrated in FIG. 11 differsfrom the first embodiment described above in that the gas channel sealis not designed in the fourth embodiment—as in the first embodiment—as aflat seal acted upon with an external clamping force but rather as aslide fit sealing.

As is apparent from the sectional illustration of FIG. 11, the channelwall area 166 of the fluid guiding frame of the first embodiment whichis aligned parallel to the stacking direction 112 is omitted in the caseof the fluid guiding frame 120″ of the fourth embodiment and so in thefourth embodiment the inner edge area 178 of the fluid guiding frame120″ merges directly into the seal contact area 162 of the fluid guidingframe 120″ without any bending line. The seal contact area 162 merges atits edge facing away from the inner edge area 178 along a bending line242 into a channel wall area 244 which is aligned parallel to thestacking direction 112 and, on the other hand, merges at its upper edgefacing away from the seal contact area 162 along a bending line 246 intoa shoulder area 248 which is aligned essentially at right angles to thestacking direction 112 and is directed into the respective port 154 or156.

The contact plate 118′ has in this fourth embodiment, in contrast to thecontact plate of the first embodiment, at each of the ports 142 and 144a collar 250 which surrounds the relevant port in a ring shape, isaligned essentially parallel to the stacking direction 112 and bordersalong a bending line 252 on the respectively adjacent inclined surface146 and the flange area 136 of the contact plate 118′, respectively.

As is apparent from FIG. 11, a respective spacer element 252 surroundingthe channel wall area 244 in a ring shape is arranged on the upper sideof the seal contact area 162 and on the outer side of the channel wallarea 244 of each fluid guiding frame 120″, this spacer element having anessentially L-shaped cross section with a first arm 254, which rests onthe seal contact area 162 and is aligned essentially at right angles tothe stacking direction 112, and with a second arm 256 which rests on theouter side of the channel wall area 244 and is aligned essentiallyparallel to the stacking direction 112.

The first arm 254 of the spacer element 252 serves as a distance piecebetween the collar 250 of the contact plate 118′ and the seal contactarea 162 of the holding plate 120″.

The second arm 256 of the spacer element 252 serves as a distance piecebetween the collar 250 of the contact plate 118′ and the channel wallarea 244 of the fluid guiding frame 120″.

The spacer element 252 consists of an electrically insulating materialwhich is rigid and resistant at the operating temperature of the fuelcell device 100 of, for example, approximately 850° C.

The spacer element 252 can, for example, be formed from Al₂O₃.

The second arm 256 of the spacer element 252 supports a sealing bead 256which surrounds the channel wall area 244 of the fluid guiding frame120″ in a ring shape and closes the gap between the channel wall area244 and the collar 250 of the contact plate 118′.

The sealing bead 258 consists of an electrically non-conductive materialwhich is viscous but chemically resistant at the operating temperatureof the fuel cell device 100 of, for example, approximately 850° C.

A solder glass or an amorphous material similar to glass can be;considered, in particular, as material for the sealing bead 256.

If the sealing bead 258 is formed from a solder glass, it can beproduced by applying a paste containing powdered glass.

When the operating temperature of the fuel cell device 100 is reached,the melted sealing bead 258 fills the gap between the collar 250 of thecontact plate 118′ and the channel wall area 244 of the fluid guidingframe 120″ in a gas-tight manner.

Possible differences in pressure between the combustible gas chamber 124and the oxidation agent chamber 130 or different heat expansions arecompensated by a displacement of the collar 250 of the contact plate118′ relative to the fluid guiding frame 120″.

This is possible without more ado since the contact plate 118′ and thefluid guiding frame 120″ are, in this embodiment, not rigidly connectedto one another but rather the collar 250 of the contact plate 118′ andthe holding plate 120″ are displaceable relative to one another alongthe stacking direction 112, namely by the distance, by which the secondarm 256 of the spacer element 252 projects beyond its first arm 254along the stacking direction 112. If the collar 250 is displacedrelative to the fluid guiding frame 120″ proceeding from the initialposition illustrated in FIG. 11 along the stacking direction 112upwards, the melted sealing bead 258 continues to provide for agas-tight sealing between the contact plate 118′ and the fluid guidingframe 120″ while the spacer element 252 prevents the viscous mass of thesealing bead 258 from running out into the oxidation agent chamber 130.

The contact plate 118′ and the fluid guiding frame 120″ are alsodisplaceable relative to one another at right angles to the stackingdirection 112, namely by the distance, by which the first arm 254 of thespacer element 252 projects beyond its second arm 256 at right angles tothe stacking direction 112. If the collar 250 is displaced relative tothe fluid guiding frame 120″ proceeding from the initial positionillustrated in FIG. 11 at right angles to the stacking direction 112,the melted sealing bead 258 continues to provide for a gas-tight sealingbetween the contact plate 118′ and the fluid guiding frame 120″.

Such a slide fit sealing at the combustible gas channel 190 and thewaste gas channel 198 is particularly suitable for compensating fordifferences between the individual components of the fuel cell units 114(CAE unit 116, contact plate 118′ and fluid guiding frame 120″) withrespect to their thermal coefficients of expansion.

Since no predetermined contact pressure is required for the slide fitsealing, it is also not necessary with this fourth embodiment—in thesame way as with the second and the third embodiments—to brace the fuelcell units 114 of the composite block of fuel cells 106 against oneanother. It is merely necessary for the fuel cell units to be fixed intheir position relative to one another and for an adequate contactpressure to be generated between the CAE units and the contact plates.

To produce the composite block of fuel cells 106 of the fourthembodiment the procedure is preferably—as with the first embodiment—suchthat first of all the individual fuel cell units 114 are connected toone another by way of a gas-tight connection of the contact plate 118′and the fluid guiding frame 12011 of the same fuel cell unit 114 and,subsequently, the assembled fuel cell units 114 are stacked on top ofone another along the stacking direction 112.

As for the rest, the fourth embodiment of a fuel cell device correspondswith respect to construction and operation to the first embodiment andin this respect reference is made to its description above.

A fifth embodiment of a fuel cell device illustrated in FIG. 12 differsfrom the fourth embodiment described above in that apart from the gaschannel seal 188″ in the fourth embodiment the combustible gas chamberseal 186′ is also designed as a slide fit sealing.

As is apparent from the sectional illustration of FIG. 12, a slopingwall area 262, which is inclined at an angle of approximately 45° inrelation to the stacking direction 112 and merges into a wall area 266curved in an shape along a bending line 264 at its lower edge facingaway from the seal contact area 162, borders on the seal contact area162 along a bending line 260 in the case of the fluid guiding frame 120″of the fifth embodiment. The wall area 266 curved in an S shape borders,for its part, at its upper edge facing away from the sloping wall area262 on the inner edge area 178 of the fluid guiding frame 120″.

As is apparent from FIG. 12, a respective spacer element 270 surroundingthe CAE unit 116 in a ring shape is arranged on the underside of theinner edge area 178 and on the side wall 268 of the CAE unit 116, thisspacer element having an essentially L-shaped cross section with a firstarm 272, which abuts on the side wall 268 of the CAE unit 116 and isaligned essentially parallel to the stacking direction 112, and with asecond arm 274 which abuts on the upper side of the CAE unit 116 and onthe underside of the inner edge area 178 of the fluid guiding frame 120″and is aligned essentially at right angles to the stacking direction112.

The first arm 272 of the spacer element 270 serves as a distance piecebetween the CAE unit 116 and the curved wall area 266 of the fluidguiding frame 120″. The second arm 274 of the spacer element 270 servesas a distance piece between the CAE element 116 and the inner edge area178 of the fluid guiding frame 120″.

The distance element 270 also consists of an electrically insulatingmaterial which is rigid and resistant at the operating temperature ofthe fuel cell device 100 of, for example, approximately 850° C., forexample, of Al₂O₃.

A sealing element 276 closed in a ring shape is arranged along the inneredge of the second arm 274 of the spacer element 270 and consists of anelectrically non-conductive material which is viscous but chemicallyresistant at the operating temperature of the fuel cell device 100 of,for example, approximately 850° C.

A solder glass or an amorphous material similar to glass can beconsidered, in particular, as material for the sealing element 276.

If the sealing element 276 is formed from a solder glass, it may beproduced by applying a paste containing powdered glass to the upper sideof the CAE element 116, for example, with the screen printing method.

Once the operating temperature of the fuel cell device 100 is reached,the melted sealing element 276 fills the entire intermediate spacebetween the inner edge area 178 of the fluid guiding frame 12011 and theCAE element 116 in a gas-tight manner.

Possible differences in pressure between the combustible gas chamber 124and the oxidation agent chamber 130 or differences with respect to theheat expansion of the individual components of the fuel cell units 114are compensated by a relative displacement between the CAE unit 116 andthe fluid guiding frame 120″.

This is possible without further ado since the CAE unit 116 and thefluid guiding frame 120″ are not rigidly connected to one another butare displaceable relative to one another at right angles to the stackingdirection 112, namely by the distance, by which the second arm 274 ofthe spacer element 270 projects beyond its first arm 272 at right anglesto the stacking direction 112.

If the CAE unit 116 is displaced relative to the fluid guiding frame120″ proceeding from the initial position illustrated in FIG. 12 atright angles to the stacking direction 112 to the left, the meltedsealing element 276 continues to provide for a gas-tight sealing betweenthe CAE unit 116 and the fluid guiding frame 120″ while the spacerelement 270 prevents the viscous mass of the sealing element 276 fromrunning out into the combustible gas chamber 124.

Such a slide fit sealing between the combustible gas chamber 124 and theoxidation agent chamber 130 is particularly suitable for compensatingfor any difference between the individual components of the fuel cellunits 114 (CAE unit 116, contact plate 118′ and fluid guiding frame120″) with respect to their thermal coefficients of expansion.

As for the rest, the fifth embodiment of a fuel cell device correspondswith respect to construction and operation to the fourth embodiment andin this respect reference is made to its description above.

1. Fuel cell unit, comprising: a cathode-anode-electrolyte unit, and acontact plate in electrically conductive contact with thecathode-anode-electrolyte unit, and a fluid guiding element being formedas a shaped sheet metal part and connected to the contact plate in afluid-tight manner, wherein the fluid guiding element is provided withat least one fluid port in a fluid guiding area of the fluid guidingelement to which the electrolyte of the cathode-anode-electrolyte unitdoes not extend, said fluid port forming a part of a fluid channel whichextends through the fuel cell unit parallel to a stacking direction andwhich does not pass through the electrolyte of the cathode-anodeelectrolyte unit. 2.-31. (canceled)
 32. Fuel cell unit as defined inclaim 1, wherein the cathode-anode-electrolyte unit is arranged on thefluid guiding element.
 33. Fuel cell unit as defined in claim 1, whereinthe contact plate is designed as a shaped sheet metal part.
 34. Fuelcell unit as defined in claim 1, wherein the fluid guiding element andthe contact plate are connected to one another by laser welding or byelectron beam welding or by hard soldering.
 35. Fuel cell unit asdefined in claim 1, wherein the fluid guiding element has an opening forthe passage of contact elements to the cathode-anode-electrolyte unit.36. Fuel cell unit as defined in claim 1, wherein the fluid guidingelement abuts on the cathode-anode-electrolyte unit via an electricallyinsulating seal.
 37. Fuel cell unit as defined in claim 36, wherein theseal comprises mica.
 38. Fuel cell unit as defined in claim 36, whereinthe seal comprises a flat seal.
 39. Fuel cell unit as defined claim 36,wherein the seal comprises a coating on at least one of the fluidguiding element and the cathode-anode-electrolyte unit.
 40. Fuel cellunit as defined in claim 1, wherein the cathode-anode-electrolyte unitand the fluid guiding element are biased elastically against oneanother.
 41. Fuel cell unit as defined in claim 1, wherein the fluidguiding element is provided with a fluid supply channel opening and witha fluid discharge channel opening.
 42. Fuel cell unit as defined inclaim 1, wherein the fuel cell unit comprises an electrically insulatingfluid channel seal, the contact plate of the fuel cell unit abutting onthe fluid guiding element of an adjacent fuel cell unit via said seal.43. Fuel cell unit as defined in claim 1, wherein the fuel cell unitcomprises a fluid channel seal, the fluid guiding element of the fuelcell unit abutting on the contact plate of an adjacent fuel cell unitvia said seal.
 44. Fuel cell unit as defined in claim 43, wherein thefluid channel seal comprises a coating on at least one of the fluidguiding element and the contact plate.
 45. Fuel cell unit as defined inclaim 43, wherein the fluid channel seal comprises a flat seal.
 46. Fuelcell unit as defined in claim 43, wherein the fluid channel sealcomprises at least two separate sealing elements.
 47. Fuel cell unit asdefined in claim 43, wherein the fluid channel seal comprises a slidefit sealing.
 48. Fuel cell unit as defined in claim 43, wherein thefluid channel seal comprises a material viscous at the operatingtemperature of the fuel cell unit.
 49. Composite block of fuel cells,comprising a plurality of fuel cell units as defined in claim 1, saidunits following one another along a stacking direction.
 50. Compositeblock of fuel cells as defined in claim 49, wherein the composite blockof fuel cells comprises at least one clamping element for bracing thefuel cell units against one another.
 51. Composite block of fuel cellsas defined in claim 50, wherein the composite block of fuel cellscomprises two end plates adapted to be braced against one another bymeans of the clamping element.
 52. Composite block of fuel cells asdefined in claim 51, wherein at least one of the end plates has at leastone fluid port.
 53. Composite block of fuel cells as defined in claim49, wherein the fluid guiding element of at least one of the fuel cellunits is connected to the contact plate of an adjacent fuel cell unit byway of flanging.
 54. Composite block of fuel cells as defined in claim53, wherein a flange fold area engaging around the contact plate of theadjacent fuel cell unit is formed on the fluid guiding element of atleast one of the fuel cell units.
 55. Composite block of fuel cell asdefined in claim 54, wherein an electrically insulating fluid channelseal is arranged between the flange fold area and the contact plate ofthe adjacent fuel cell unit.
 56. Fuel cell unit as defined in claim 1,wherein the cathode-anode-electrolyte unit is held between the fluidguiding element and the contact plate.
 57. Fuel cell unit as defined inclaim 48, wherein the fluid channel seal comprises a solder glass. 58.Fuel cell unit as defined in claim 1, wherein said fluid guiding elementand said contact plate form a two-part shell surrounding saidcathode-anode-electrolyte unit of the fuel cell unit.
 59. Fuel cell unitas defined in clam 1, further comprising an electrically insulatingfluid channel seal arranged between the contact plate of the fuel cellunit and the fluid guiding element of an adjacent fuel cell unit orbetween the fluid guiding element of the fuel cell unit and the contactplate of an adjacent fuel cell unit, said fluid channel seal surroundinga fluid port provided in the fluid guiding element or a fluid portprovided in the contact plate and said fluid channel seal being spacedapart from the electrolyte of the cathode-anode-electrolyte unit of thefuel cell unit.
 60. Fuel cell unit as defined in claim 1, wherein saidfluid guiding element forms a boundary of a fluid chamber having fluidflowing through it during operation of the fuel cell unit.
 61. Fuel cellunit as defined in claim 1, wherein said fluid guiding element isconnected to the contact plate by way of welding or by way of soldering.62. Fuel cell unit as defined in claim 1, wherein said fluid guidingelement and said contact plate define therebetween a fluid chamberhaving a combustible gas or an oxidation agent flowing through it duringoperation of the fuel cell unit.
 63. Fuel cell unit, comprising: acathode-anode-electrolyte unit, a contact plate in electricallyconductive contact with the cathode-anode-electrolyte unit, and a fluidguiding element being formed as a shaped sheet metal part and connectedto the contact plate in a fluid-tight and electrically conductivemanner, said fluid guiding element having an opening for the passage ofcontact elements arranged on a contact plate of an adjacent fuel cellunit to the cathode-anode-electrolyte unit of the fuel cell unit. 64.Fuel cell unit as defined in claim 63, wherein thecathode-anode-electrolyte unit is arranged on the fluid guiding element.65. Fuel cell unit as defined in claim 63, wherein the contact plate isdesigned as a shaped sheet metal part.
 66. Fuel cell unit as defined inclaim 63, wherein the fluid guiding element and the contact plate areconnected to one another by laser welding or by electron beam welding orby hard soldering.
 67. Fuel cell unit as defined in claim 63, whereinthe fluid guiding element has an opening for the passage of contactelements to the cathode-anode-electrolyte unit.
 68. Fuel cell unit asdefined in claim 63, wherein the fluid guiding element abuts on thecathode-anode-electrolyte unit via an electrically insulating seal. 69.Fuel cell unit as defined in claim 68, wherein the seal comprises mica.70. Fuel cell unit as defined in claim 68, wherein the seal comprises aflat seal.
 71. Fuel cell unit as defined in claim 68, wherein the sealcomprises a coating on at least one of the fluid guiding element and thecathode-anode-electrolyte unit.
 72. Fuel cell unit as defined in claim63, wherein the cathode-anode-electrolyte unit and the fluid guidingelement are biased elastically against one another.
 73. Fuel cell unitas defined in claim 63, wherein the fluid guiding element is providedwith a fluid supply channel opening and with a fluid discharge channelopening.
 74. Fuel cell unit as defined in claim 63, wherein the fuelcell unit comprises an electrically insulating fluid channel seal, thecontact plate of the fuel cell unit abutting on the fluid guidingelement of an adjacent fuel cell unit via said seal.
 75. Fuel cell unitas defined in claim 63, wherein the fuel cell unit comprises a fluidchannel seal, the fluid guiding element of the fuel cell unit abuttingon the contact plate of an adjacent fuel cell unit via said seal. 76.Fuel cell unit as defined in claim 75, wherein the fluid channel sealcomprises a coating on at least one of the fluid guiding element and thecontact plate.
 77. Fuel cell unit as defined in claim 75, wherein thefluid channel seal comprises a flat seal.
 78. Fuel cell unit as definedin claim 75, wherein the fluid channel seal comprises at least twoseparate sealing elements.
 79. Fuel cell unit as defined in claim 75,wherein the fluid channel seal comprises a slide fit sealing.
 80. Fuelcell unit as defined in claim 75, wherein the fluid channel sealcomprises a material viscous at the operating temperature of the fuelcell unit.
 81. Composite block of fuel cells, comprising a plurality offuel cell units as defined in claim 63, said units following one anotheralong a stacking direction.
 82. Composite block of fuel cells as definedin claim 81, wherein the composite block of fuel cells comprises atleast one clamping element for bracing the fuel cell units against oneanother.
 83. Composite block of fuel cells as defined in claim 82,wherein the composite block of fuel cells comprises two end platesadapted to be braced against one another by means of the clampingelement.
 84. Composite block of fuel cells as defined in claim 83,wherein at least one of the end plates has at least one fluid port. 85.Composite block of fuel cells as defined in claim 81, wherein the fluidguiding element of at least one of the fuel cell units is connected tothe contact plate of an adjacent fuel cell unit by way of flanging. 86.Composite block of fuel cells as defined in claim 85, wherein a flangefold area engaging around the contact plate of the adjacent fuel cellunit is formed on the fluid guiding element of at least one of the fuelcell units.
 87. Composite block of fuel cells as defined in claim 86,wherein an electrically insulating fluid channel seal is arrangedbetween the flange fold area and the contact plate of the adjacent fuelcell unit.
 88. Fuel cell unit as defined in claim 63, wherein thecathode-anode-electrolyte unit is held between the fluid guiding elementand the contact plate.
 89. Fuel cell unit as defined in claim 80,wherein the fluid channel seal comprises a solder glass.
 90. Fuel cellunit as defined in claim 63, wherein said fluid guiding element and saidcontact plate form a two-part shell surrounding saidcathode-anode-electrolyte unit of the fuel cell unit.
 91. Fuel cell unitas defined in claim 63, further comprising an electrically insulatingfluid channel seal arranged between the contact plate of the fuel cellunit and the fluid guiding element of an adjacent fuel cell unit orbetween the fluid guiding element of the fuel cell unit and the contactplate of an adjacent fuel cell unit, said fluid channel seal surroundinga fluid port provided in the fluid guiding element or a fluid portprovided in the contact plate and said fluid channel seal being spacedapart from the electrolyte of the cathode-anode-electrolyte unit of thefuel cell unit.
 92. Fuel cell unit as defined in claim 63, wherein saidfluid guiding element forms a boundary of a fluid chamber having fluidflowing through it during operation of the fuel cell unit.
 93. Fuel cellunit as defined in claim 63, wherein said fluid guiding element isconnected to the contact plate by way of welding or by way of soldering.94. Fuel cell unit as defined in claim 63, wherein said fluid guidingelement and said contact plate define therebetween a fluid chamberhaving a combustible gas or an oxidant agent flowing through it duringoperation of the fuel cell unit.